1. Field of the Invention
The present invention relates to a data processing apparatus, system control method and system. More particularly, the invention relates to control at power shutdown in a data processing apparatus that is capable of executing processing of a shared job requiring cooperative operation using another data processing apparatus.
2. Description of the Related Art
An apparatus referred to as a multifunction peripheral (MFP) has been developed as office automation (OA) equipment in recent years and joins such devices as image readers (scanners) and copiers. An MFP has multiple functions such as a scanning function, copying function, facsimile function and printing function.
In an effort to exploit the functions of such OA equipment effectively, it has been proposed to execute a variety of shared jobs by utilizing a plurality of devices connected to a network.
For example, cascade copying is known in the art and is executable in a system having an image reader, a first MFP locally connected to the reader and a second MFP connected to the first MFP via a network. Cascade copying is a job in which image data that has been scanned in by the image reader is printed simultaneously by the first and second MFPs.
Further, “remote copying” is also commonly performed. Remote copying utilizes an image reader and a printing apparatus (printer) connected via a network. Image data that has been scanned in by the image reader is transmitted to the printing apparatus via the network, and the printer apparatus performs printing based upon the image data.
It is predicted that such shared jobs will increase greatly in the future. For example, shared jobs are effective in a case where high-value optional functions are shared by a plurality of devices over a network. These high-value options make possible various types of image processing such as PDF processing, TIFF processing, OCR processing, compression/expansion processing and encryption processing. In a concrete example of such a shared job, image data that has been acquired by a local device is transmitted to a specific remote device via a network and is subjected to image processing by shared optional functions. The image data sent back is subsequently stored in the local device or printed out.
A shared job referred to as “pull printing” also is possible. In pull printing, image data that has been stored in a remote device is retrieved by a local device via a network, this image data is transmitted to the local device and is printed by the local device.
Although it is possible to shut down (turn off) the power supply of each device that takes part in executing such shared jobs, the timing at which the power supplies are turned off is difficult.
The specification of Japanese Patent Application Laid-Open No. 2004-241864 describes processing at power shutdown in two image processing devices that operate in tandem as master and slave. If the power supply of the master device has been turned off, the slave device abandons the scheduled job, moves up the succeeding job and executes it preferentially. If the power supply of the slave device is turned off, on the other hand, the master device is decoupled from the slave device and operates independently.
However, master and slave roles are not fixed in a device that takes part in executing a shared job. That is, there are cases where even though the device operates as a master in relation to a certain shared job, it operates as a slave in relation to another shared job. This means that it is difficult to apply processing of the kind described in the prior-art application mentioned above.
If the power supply of either device is forcibly turned off during execution of a shared job, a mismatch occurs between the devices during execution of the shared job, the shared job is suspended and an error occurs in the worst case.
On the other hand, in order to avoid power shutdown during execution of a shared job, the status of job execution must be monitored at all times. If shared jobs are requested one after another from other devices connected over the network in such case, there will no longer be a break between shared jobs and it will be difficult to shut down power.